The present invention relates to a method of communication between an arbitrary number of remote terminals and a central station, the terminals and the central station being interconnected by way of a communication path having an outgoing communication channel between the central station and the remote terminals and an incoming communication channel in the reverse direction. This invention is particularly useful in all situations in which costly computations should be made, which require very high computing powers, for example those carried out in meteorology, or in applications such as the decoding of the human genome, aeronautical computations etc.
The growing interest in communication networks has induced researchers and the industry to develop so-called multimedia applications for the users. Since the additional possibilities provided by these applications (notably, interactivity and two-way communication) are not always based on standardized communication protocols, the MPEG group (Moving Pictures Expert Group) of the ISO (International Organization for Standardization) has endeavored to structure and standardize the processes of encoding and synchronization of transported information. Although this standard, which is named MPEG-4 and which is to be issued in 1998, competes with other solutions, it is likely that, in any case, the digital encoding terminals provided at the users will be equipped with powerful functions, particularly in order to enable the implementation of the additional possibilities mentioned above.
It is an object of the invention to provide a method of communication between a central server and remote terminals, which enables the remote terminals to be used in a novel manner as compared with their primary function, by conceiving more uses than those required for the simple application for which they were originally intended.
To this end, according to the invention, a communication method of the type defined in the opening paragraph of the description, is characterized in that the remote terminals are consumer products, respective individual users being able to start the activation of their corresponding principal function, and the method includes the following steps:
(A) a test step for the reception, by any one of the remote terminals, of a request for the activation of the remote terminal, which is addressed by the central station to start the activation of an auxiliary function which is autonomous with respect to the principal function;
(B) a test step for the availability and authorization for use, to transmit to the central station information relating to the availability of the remote terminals so requested;
(C) a step of transmitting data to the available remote terminals, the data relating to operations requested from these terminals by the central station in the scope of said auxiliary function;
(D) a step of carrying out the operations and returning the results of the operations carried out to the central station.
The principle of this method is as follows. On the one hand, these remote terminals have been (or, rather will be, because at present the decoding circuits are only cabled) provided with a return channel, i.e. a communication means between the remote terminals and the central server to which they are connected, so as to provide the interactivity. On the other hand, each of the remote terminals has (or will have) a powerful programmable multimedia processor, the functions of decoding, interactivity etc. being provided by software run on the processor. Finally, each remote terminal can be identified (the presence of an identification means is indispensable, for example, to effect deciphering in the case of coded or pay transmissions). When a remote terminal is not used for its principal function and it user does not prohibit this new activity, all these functions enable it to be employed in an alternative manner to realize a variety of functions, particularly computing functions. The computing power thus obtained can be very impressive at a minimal cost, providing that the operations or calculations to be carried out allow a modular division into small units which can be processed independently of one another.
It has already been proposed to replace an encoder of the MPEG-2 type by a combination of parallel work stations so as to assure a coordinated implementation of the MPEG-2 encoding algorithm. The document xe2x80x9cSoftware implementation of MPEG-II video encoding using socket programming in LANxe2x80x9d, Y. Yu et al., Proceedings of the SPIE, Int. Soc. Opt. Eng. (USA), Vol. 2187, pp. 229-240, describes such a solution. However, in the application, the principal function performed by the stations which operate in parallel remains the same as that originally envisaged and the described encoding means merely assure that, in contradistinction to what has been proposed in the case of the invention, the same principal function is carried out in, what may be called, an equivalent form.
In a special variant of the invention, the communication protocol thus defined provides means for the individual response of each remote terminal to the request send to it by the server. To this end, the method in accordance with the invention is characterized in that step (B) comprises a first test for activity of the remote terminal or remote terminals which have received an activation request, a second test for authorization to use the remote terminal for another activity, and an operation of responding to the central station in a time window specific to this terminal, to report its state of availability to said station.
When this variant is adopted, the method is preferably characterized in that the operation of addressing of each remote terminal by the central station is realized with the aid of an identification code for this remote terminal, and the specific position of the time window is defined by the identification code.
Regardless of the proposed variant, it is always particularly favourable that the central station transmits data of the application to be carried out to each available remote terminal in a language which is independent of the type of the relevant remote terminal.
Moreover, as in the case of the afore-mentioned variant, it is advantageous that in the implementation of the method step (D) is also effected in a time window specific to each of the remote terminals which have made themselves available.
Finally, in an improved variant of the method, in the case of activation of the principal function of a remote terminal, it also includes a step of storing the current state assumed by the respective terminal as a result of the progress of steps (A) to (D) when the auxiliary function has been activated.